1. Field of the Invention
The present disclosure relates to an optical disk medium in which data is optically recorded, and a recording method and an optical disk apparatus for recording and reproducing the data in and from the optical disk medium.
2. Description of the Related Art
Currently, various types of optical disks such as a DVD and a Blu-ray (registered trademark) disk (hereinafter, referred to as a BD) have been used as an information recording medium for storing a video image and data. These optical disks have higher storage reliability than a Hard Disk Drive (hereinafter, referred to as an HDD) or a magnetic tape. Therefore, usage of the optical disk is expanding from conventional storage of AV (Audio and Video) data such as a video image and a sound to long-term data storage.
However, a capacity of the data that can be stored per volume of the optical disk is about one-third of the HDD or magnetic tape. Therefore, from the viewpoint of space efficiency during storage, there is a demand for improving the capacity of the data that can be stored per volume without increasing cost of the optical disk, and research and development is actively continued. Recently, among BDs, a BDXL disk having recording density of about 33.4 GB per layer is released as an optical disk having the highest volume recording density.
Such an optical disk can store data for at least 50 years, and the optical disks have the storage reliability greater than or equal to 10 times a lifetime of about 5 years of the HDD from the viewpoint of long-term data storage. The data for the long-term storage is transferred from the HDD to the optical disk, which allows a balance between the long-term storage reliability and reduction of storage cost to be established. Particularly, compared with the HDD in which the power is consumed during data storage, in the optical disk in which no power is required during the data storage, an amount of carbon dioxide emission can be reduced as a green storage, and therefore data center power consumption that becomes a major issue can be reduced.
However, even in the BDXL disk having the highest recording density among the optical disks, the capacity of the data that can be stored per volume is about one-third of the HDD. Compared with the HDD, more storage space is required for the optical disk during the data storage. Particularly, for the usage in a data center where cost demands related to a storage space are high, there is a demand for improving the recording density per volume of the optical disk.
A land (inter-groove)-groove recording and reproducing technology of being able to improve the recording density of a track is well known as the technology of improving the recording density per volume of the optical disk. The land-groove recording and reproducing technology is already applied to DVD-RAM. In the land-groove recording and reproducing technology, the recording density of the track is improved by recording the data, which is recorded in the land or the groove in the conventional technology, in both the groove and the land.
However, in the DVD-RAM, because a data recording region and an address region are provided in the track, format efficiency is degraded to waste a region where the data is recorded. Therefore, there is disclosed a technology of recording address information by wobbling of a groove track to make good use of the data recording region (see PTL 1).
According to PTL 1, in the address information recorded by the wobbling of the groove track, an inner circumference is equal to an outer circumference in a number of pieces of address information per track, and the density of the address information per track length decreases gradually toward the outer circumference. When the data recorded in the optical disk medium having the above configuration, in order to keep the recording density constant in a recording surface of the optical disk medium, the recording surface of the optical disk medium is radially divided into a plurality of zones for managing recording. Specifically, in generating a recording clock used to record the data from a wobble signal obtained by the wobbling of the track, a frequency of the recording clock to a frequency of the wobble signal is set to a predetermined multiplying factor in accordance with a radius ratio, whereby the recording density is substantially kept constant in each zone. Therefore, although the optical disk medium has a structure in which the wobbling and the address are radially arranged, the recording density can substantially be kept constant from the inner circumference to the outer circumference by dividing the recording surface into the plurality of zones.
FIG. 6 is a view illustrating an arrangement structure of the data and the address with respect to an optical disk medium that is the conventional technology disclosed in PTL 1. FIG. 6 illustrates the arrangement structure near a boundary of zones A−1 and A adjacent to each other. In zone A−1, a range of ADIP (ADdress In Pregroove) indicating an address expressing a position of the track arranged by wobbling is N−4, N−3, N−2, and N−1. In zone A, the range of the ADIP is N, N+1, N+2, and N+3. In the optical disk medium, a length of the ADIP is different from a length of the data to be recorded. Therefore, a one-on-one relationship does not hold between the ADIP and a data address. During continuous recording and management of the data to be recorded in any zone, a recording start position is fixed from the ADIP when the data is initially recording in any zone, and an additional recording start position is fixed from data address information on the recorded data to perform linking recording when the data is additionally recorded in the same zone. Therefore, the data can be recorded even if the length of the ADIP is different from the length of the data.
FIG. 7 is a view illustrating a configuration of optical disk apparatus 70 in PTL 1 that is a conventional technology. Referring to FIG. 7, optical disk apparatus 70 includes optical disk medium 700, optical head 701, spindle motor 702, servo controller 703, reproducing PLL (Phase Locked Loop) circuit 704, data demodulating circuit 705, error correction decoding circuit 706, laser driving circuit 707, data modulating circuit 708, error correction coding circuit 709, wobble detecting circuit 710, wobble PLL circuit 711, channel PLL circuit 712, ADIP reproducing circuit 713, system controller 714, InterFace (I/F) circuit 715, and host 716.
Spindle motor 702 rotates optical disk medium 700. Optical head 701 records the data in optical disk medium 700, and reproduces the data from optical disk medium 700.
Servo controller 703 controls optical head 701 and spindle motor 702, performs control for focusing a light beam emitted from optical head 701 onto optical disk medium 700 and for scanning optical disk medium 700 with the light beam, and performs moving control for gaining access to the target track.
I/F circuit 715 receives recording data to be recorded in optical disk medium 700 from host 716, and transmits reproducing data reproduced from optical disk medium 700 to host 716.
Error correction coding circuit 709 adds parity for error correction to the recording data received from I/F circuit 715.
Data modulating circuit 708 modulates the recording data including the parity from the error correction coding circuit 709 in accordance with a predetermined modulation rule, and converts the recording data into a recording pattern recorded on optical disk medium 700.
In order to correctly form a mark on optical disk medium 700, laser driving circuit 707 converts the recording pattern modulated by data modulating circuit 708 into an optical pulse to drive a laser of optical head 701.
Wobble detecting circuit 710 filters and extracts a wobble signal from the reproducing signal of optical disk medium 700.
Wobble PLL circuit 711 multiplies the wobble signal at a predetermined multiplying factor to generate a wobble clock.
ADIP reproducing circuit 713 reproduces ADIP information from the wobble signal and the wobble clock.
Channel PLL circuit 712 is operated such that a phase of a clock in which the wobble clock is divided by m is synchronized with a phase of a clock in which the recording clock is divided by n, and channel PLL circuit 712 generates the recording clock having an n/m frequency.
Reproducing PLL circuit 704 extracts a synchronization clock for demodulating the reproducing signal from optical disk medium 700.
Data demodulating circuit 705 demodulates the recorded data from the reproducing signal.
Error correction decoding circuit 706 corrects an error of the demodulated data and restores.
System controller 714 controls each block, and also controls communication with host 716. System controller 714 controls each unit of optical disk apparatus 70 such that the data is recorded based on the recording clock generated by channel PLL circuit 712. Data modulating circuit 708, laser driving circuit 707, and optical head 701 record the data based on the recording clock.
A recording operation of optical disk apparatus 70 will be described below. I/F circuit 715 acquires the recording data transmitted from host 716. Error correction coding circuit 709 adds a parity code for correcting the error during the reproducing, to the recording data transferred through I/F circuit 715. For example, data modulating circuit 708 modulates the recording data to which the parity code is added to the recording pattern in accordance with a modulation rule of a 1-7 PP code that is one of run-length limited codes. Laser driving circuit 707 converts the recording pattern, which is modulated to a recording mark and a space of 2 T to 9 T by the 1-7 PP code, into a castle type pulse waveform in order to correctly form the recording mark on optical disk medium 700, and laser driving circuit 707 outputs to optical head 701 a driving signal for driving the laser. Optical head 701 irradiates optical disk medium 700 with a laser pulse to record the recording pattern.
Optical disk medium 700 has a structure in which the ADIP is radially provided. Therefore, the recording clock used to record the data is controlled such that line density of the recording data is substantially kept constant in the recording surface of optical disk medium 700. Channel PLL circuit 712 controls the recording clock. Wobble detecting circuit 710 detects a wobble signal corresponding to the wobbling of the track. Based on the wobble signal, wobble PLL circuit 711 generates the wobble clock synchronized with the wobble signal. Channel PLL circuit 712 is operated such that a phase of a clock in which the wobble clock is divided by m is synchronized with a phase of a clock in which the recording clock is divided by n, and channel PLL circuit 712 generates the recording clock having the n/m frequency of the wobble clock.
The recording surface of optical disk medium 700 is radially divided into the plurality of zones. In each of the plurality of zones, the frequency of the recording clock or the recording density is changed. At a starting position of each of the plurality of zones, system controller 714 fits the recording start position of the recording pattern recorded in optical disk medium 700 to a boundary of the ADIP. In additionally recording the recording pattern in the zone, data demodulating circuit 705 demodulates the already-recorded recording pattern, and detects a synchronization mark and the data address, which are included in the recording pattern, to identify the position to an accuracy of 1T. Based on the position identified by data demodulating circuit 705, the recording pattern to be newly recorded is recorded so as to be continuous with a terminal position of the already-recorded recording pattern. The continuous writing of the data enables the recording data in the zone to be reproduced without interruption while the data address is detected to confirm continuousness.
In a neighborhood of the boundary of zones A−1 and A in FIG. 6, the recording pattern is continuously recorded in data addresses M−2 and M−1 in zone A−1. At the starting position of zone A, the boundary of ADIP N is coincides with the boundary of data address M of the recording pattern, and the recording pattern is continuously recorded in data address M+1. In the case that the further recording pattern is newly recorded, the recording pattern is continuously recorded in data address M+2.
According to the conventional method in FIG. 6, the data can be recorded in the same optical disk medium while the data line density is changed. For example, the data can be recorded in the optical disk with the same line density as BDXL, the data can be recorded in the optical disk at 1.2 times the data line density of BDXL, and the data can be recorded in the optical disk at twice the data line density of BDXL. Therefore, a capacity of the optical disk medium can be increased only by a technology of processing the recording and reproducing signals without changing the substantial structure of optical disk medium, and the storage cost can be reduced.